Encoded information reading (EIR) terminals equipped with wireless communication interfaces are widely used in retail stores, shipping facilities, etc. The protocol most widely used for providing data communications within the data collection system employing EIR terminals is Internet Protocol (IP) version 4. The routing scheme of IPv4 determines the destination network information from the destination IP address of a datagram. This can be analogized to the “old” phone numbering scheme (which became out-of-dated with the introduction of phone number portability), where an area code and a three-digit prefix determined the geographical location of the land-line phone. Whenever a land-line phone subscriber moved from a geographical zone served by one local exchange to a geographical zone served by another local exchange, the subscriber's phone number would change to satisfy the area code and local exchange-based numbering scheme. An IPv4 address consists of network address bits and host address bits, as defined by a netmask. Continuing the analogy, the network address bits can be considered playing the role of the area code and local exchange part of the phone number. Hence, whenever a networked device moves out of the zone served by the network defined by the network address bits of the device's IP address, the device must change its IP address, since IPv4 routing would not work and IP datagrams to the device would not be delivered if the device is connected to a network whose network address is different from the network part of the device's IP address.
The requirement of changing the IP address by a roaming device is not of a great concern unless the device, e.g., an EIR terminal equipped with a wireless network interface, moves from one network to another while at least one communication session (e.g., a TCP connection) in which the terminal participates, is active: the TCP connection would be lost immediately upon the terminal changing its IP address.
Accordingly, there is a need for a method of keeping the active communication session alive while a wireless networked device, e.g., an EIR terminal, is roaming from one network to another.
The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views.